This invention relates to determining a close point of a glide head, which is used in disk drive technology.
High performance magnetic rigid discs usually require a dedicated landing zone to optimize tribological performance while supporting low glide height. Laser texturing techniques have been introduced to create such a landing zone. The pattern of laser texture bumps often consists of a constant pitch in both circumferential and radial directions. However, during take-off and landing the head often experiences a quite different interface dynamic compared to a traditional mechanical texture.
A glide test is a process that computer hard disc drive manufacturers use to control and assure the quality of media. The glide head often consists of a piezoelectric transducer (PbZr.sub.1-x Ti.sub.x O.sub.3 PZT) mounted on an air bearing slider, but the size, shape, and mounting location of the PZT may vary. During the glide test process, the glide head flies over a disc surface at a predetermined clearance from the disc surface, also known as glide height. If contact occurs between the glide head and a disc asperity or a defect, the glide head is forced to vibrate and deform. The slider deformation results in the PZT deformation, and a potential difference is generated between the electrodes of the PZT. When the contact occurs, many vibration modes of the PZT and slider are excited simultaneously, and each mode generates a voltage at its specific frequency. Signal generated from the PZT are fed to a pre-amp and a band pass filter. A digital data acquisition system on the glide tester then processes the filtered data to compute the RMS value. The RMS signals can be used to calculate the glide avalanche breaking point (GABP) as well as to determine whether the disc passes or fails glide test. If the magnitude of the RMS voltage exceeds a predetermined threshold level, the disc is rejected.
During glide avalanche measurement at the LZT, periodic laser bump excitation and its high order harmonics may excite the natural frequency of the glide head. It can cause enormous signal read out which would mislead the reading of GABP.
With the increase of disc drive storage areal density, the fly height of a slider decreases substantially. The requirement for high quality rigid disc media without defects or asperities becomes very stringent. To meet this challenge, the design of glide heads needs to satisfy the following objectives:
1) The head fly height is sensitive to linear velocity. PA1 2) The head is able to maintain a stable flying height down to 0.5.mu. inch.
Objective (1) is typically achieved by deploying the catamaran air bearing design. Objective (2) is achieved by reducing the width of the air-bearing surface. However, to measure such a low fly height poses another challenge. In general, a fly height tester cannot measure the slider fly height at the edge. Consequently, one would measure the fly height at the 1 mil point, that is one mil from the edge. However, the fly height at the 1 mil point is higher than the one at the close point (Cp). The difference between the 1 mil point and close point depends on the head crown, head pitch, and roll.
A system is needed to improve the reliability of measuring the close point for a glide head.